Resistor construction



oct. 15, 1940. J, MARSTEN 2,218,204

RESISTOR CONSTRUCTION Filed July 19, 1935 3 Sheets-'Sheet Vl INVENTOR RN EY Oct. 15, 1940. J, MARsTgN .2,218,204

RESIsToR CONSTRUCTION Filed July 19, 19:55 s "sheetssheet 2 Jfssf ,4,75 TEN @SBM ATTORNEY 0t- 15, 1940- Y. J. MARsTEN 2 213204 RESISTOR CONSTRUCTIO Filed .my 19, 1955 s simu-shut s" MSL Patented Oct. 15, 1940 UNITED. STATES PATENT vOFFICE.

nnslsroa CONSTRUCTION a Jesse Marsten, Philadelphia, Pa., assignor to International Resistance Company, Philadelphia, Pa., a corporation of Delaware Application July 19, 1935, serial No'. 32,146

6 Claims.

This invention relates to a resistor construction. v

One of the objects of this invention is to provide a simple and practical resistor which is sturdy' and durable in construction. Another object is to provide a. resistor of the above chareasy and quick assembly. Another object is to l provide a resistor of the above character which may be produced from inexpensive materials with a marked saving of labor resulting in low cost of manufacture. Another object is to provide a resistor of the above character having high current carrying capacity in spite of the low critical temperature of some of the parts thereof. Another object is to provide a resistor of the above character utilizing a covering hermetically sealing delicate parts thereof against outside conditions. Another object is to provide a resistor of the above character, the temperature of which is maintained substantially constant throughout its length. Another object is to provide in a resistor of the above character and with an outer covering of material having al low critical temperature, means for cooling said covering to prevent deterioration thereof. Other objects will/be in part obvious and in part point-l ed out hereinafter. o

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described,v and the scope ofthe application of which will beindicatedtin the following claims.

In the accompanying drawings, in which are shown' several of the possible embodiments of this invention,

Figure 1 is a plan view of a resistance device with terminals applied thereto and without an outer covering; Figure 2 is a horizontal cross-section of the device shown in Figure 1 with the covering applied thereto;

Figure 3 is an enlarged longitudinal vertical sectional view of my resistor;

4Figure 4 is a lateral vertical sectional 'view of my resistor;

Figure 5 is a top plan view of my resistor as mounted on a panel or the like;

Figure 6 is a longitudinal vertical sectional `of my invention;

vfrom weather conditions under which the redevice cannot develop an undue amount of 'heat during operation without seriously damaging the ance device, a fiber core havingresistance wire (Cl. 20L-67) View of a resistor forming of my invention;

Figure 7 is a lateral vertical'sectional view of the resistor shown in Figure 6;

Figure 8 is a top vplan view of the resistor, 5

shown in Figure 6 as mounted on a panel or the like; I

` Figure 9 is a longitudinal vvertical sectionalview of. a resistor forming another embodiment another embodiment l 1`o` Figure 10 is a lateral vertical sectional view of the resistor shown in FigureA 9;

Figure 11 is aside elevational' View` of the. re-v sistor shown in Figure 9;

Figure v12 is a longitudinalvertical sectional 15 view of a resistor forming a further embodiment of my invention; f

Figure 13 isa longitudinal verticalseotional view of the resistor shownv in Figure` 12, taken on a line closer tothe points where'the terminals 2() project from the sides thereof;

Figure 14 is a side elevational view of the resistor shown in Figure'12, and

Figure 15 isa lateral vertical sectional view of the resistorv shown in Figure 12.

Similar reference characters refer to similar` parts throughout the several views of the drawings.-

To facilitate a better understanding of several of the features o f this invention, .some oi? the deficiencies of resistor construction eliminated by this invention will be described. It is most important to seal the resistor device per se, as well as the contacting portions of the terminals,

35 ssistor unit must operate. Iiv such a seal is not provided, rapid deterioration of the parts results, and outside humidity conditions may make for serious variations in the resistancel value of the unit during operation. Phenolic condensation products are admirably suited'A for use as such a sealing medium to encasev the resistance device" f and protect it against the above-mentioned'outa side conditions. However, .such products have a low critical temperature and thus the resistance resistor unit. Furthermore, for economical reasons, it isoften desirable to provide as a resist- Accordingly resistor units having a covering of phenolic condensatiomproduct Vor acore of such and thus their ileld of use is limited. One ofthe objects ofthis invention is to provide a resistor in which the severaldifiiculties mentioned above are remedied'in a practical manner.

Referring first to Figure 1, there is shown a fiat elongated strip i0 which may be formed from any suitable fibrous material having good kelectrical insulating characteristics. For purposes of economycf structure, an inexpensive ilbrous material is generally used, and such material has, as a rule, a low critical temperature.

The expression critical temperature," as used hereinbefore or hereinafter, signines the temperature at which a given material will commence to deteriorate as by partial or complete disintegration or decomposition.

A resistance wire ii is .wound about strip il in any suitable manner, this extending from end to end thereof. Wire ii may have any desired resistance value according to the purposeV for which the resistor unit is designed, and the' turns thereof may be close together or substantially spaced apart, this also depending-upon the resistance value desired in the -completed unit. Usually an uninsulated wire is used for' this purpose and accordingly the individual turns of wire il are maintained in spaced relationship. Strip i0 is desirably just soft enough to allow the individual turns of Wire i i to become slightly embedded therein so that they will not slip out of their spaced position after the winding operation.

Any suitable number of terminals' generally indicated at i2 are connected to strip il to contact wire ii at the desired points along the strip. Terminals .i2 may be of any desired construction, hut are preferably formed from sheet metal which is a good electrical conductor, and have-projections i3 (Figure l) extending away from the strip; projections i3 are preferably provided With apertures I4 so that they may be suitably connected4 to conductors.

As best shown in Figure 4, terminals i2 comprise a bottom portion i5 extending over a portion of the bottom of strip I0, a section i8 thereof being bent back upon portion i5. Section il extends about the strip, terminating in an outer longitudinal edge i1. Thus section i8 of the terminal-is clamped upon strip'il and makes a ilrm contact with the turns of wire ii resting therebeneath. v

An insulating block generally indicated at i8 -is preierabl'y'molded about strip Il and the connecting portions of terminals i2, as better shown in Figures 3, and 4. Block i8 preferably encases strip i0 in its entirety, thus protecting wire further prevents any movement ofthe turns of wire ii along the strip after assembly "formed in the bottom of block il.

aaiaaos of the knocks or jolis which the unit ma! rei ceive in use.

Although block Il may take any convenien shape, it is preferably provided with a fiat bottom il and a longitudinal channel 2l formed in the top thereof. Thus channel 2l has longitudinal walls 2la and 2lb and a bottom 2lc. vPreferably a longitudinal'shelf-like portion 2l is Provided in lthe side of block il adjacent the projecting portions .il of terminalsil (Figure 4). Thus a portion ila of projections Il rests upon shelflike portion 2| of the block, the projections preferably extending therefrom at right angles. although it will be understood that the projections may be bent in any direction according to the position which the completed unit occupies in use. If, however, projections Il are bent downwardly, as viewed in Figure 5, shelf-like portion 2i of the block reenforces portion ila of the terminals, helping to maintain it in a substantially horizontal `position so that the block will not be broken down or cracked at this point; such cracking might form a leak through the block into the interior of the imit.

As best shown in Figures 3 and 4, a metallic heat distributor generally indicated at 22 is cmbedded in block il. Distributor 22 is preferably formed from a metal having high heat conducting characteristics and is generally U'shaped in cross-section (Figure 4) having its top and bottom portions 2l and 24 in alinement with the opposite fiat surfaces of strip il and in close proximity thereto. 'I'he vertical or closed portion 2l of distributor 22 is adjacent the side of strip il opposite projections il so that portions ila of the projections extend through the open side of the distributor, as more clearly shown in Figure 4. A fibrous insulating strip iliFlgures 3 and 4) is wrapped about strip il over wire i i and terminals I 2 and thus prohibits passage of current from the terminals and wire to the distributor. When the resistor unit is in operation, wire ii being a resistance wiregenerates heat, and a large portion of this heat is transferred to the distributor because of its close proximity to the strip iii.

A metallic strip generally indicated at 21 (Figures 3, 4 and 5) has a longitudinal portion 2l fitting within channel 2li (Figure 4). Strip 21 preferably has'upturned edges 2l and 30 engaging walls 20a and 20h of the channel. As more clearly shown in Figures 3 and 4, the opposite end portions of strip 21 are bent downwardly to form vertical portions Il and 32 (Figure 3) in substantial engagement with the opposite ends of block il. The end portions of the strip are thence bent outwardly to form substantially horizontal fastening portions 33 and 34. Strip 21 is preferably attached to block Il by projections 35 and ll extending into notches l1 and ll Thus strip 21 extends over a-slmstantial portion of the top of block i8, as well as the opposite ends thereof, and is firmly secured thereto. End portions ll and 34 of the strip preferably are provided with suitable apertures ll and 40 (Figure 3) through which suitable rivets 4i and 42 or the like may extend to hold the unit in its operating position. Preferably' the unit is .thus connected by way of rivets A4i and 42 to a metal plate 4l or the like, the metal thereof having high heat conducting characteristics.

In operation, with current passing through wire ii, the natural tendency of the wire would be to develop various hot points along strip il. However, a large portion of the heat thus generated due to its high neat conductivity, the distributor remains at a substantially uniform ytemperature along its length. 'Accordingly it might beV said that during operation, distributor 22 operates to continually drawl heat away from potentialhot points along the strip and distributes heat evenly throughout asubstantial portion of the length of the unit.

Without 4distributor 22, the capacity of the resistor unit would be determined by the tempera.- ture of the ,hotpoints developed along the strip; the current carrying capacity of the unit would thus be limited to the amountof current which could be passedtherethrough without raising any point on the strip above the critical temperatures of strip III or block I8. With distributor 22 and ,no local peak temperatures at any point along the length of the unit, the greater portion of the length of the unit may be raised to a point just below -`the` above-mentioned critical temperatures, In other Words, the wire I I may generate a much larger total quantity of heat, and as the quantity of such heat isproportional to the amount of current passing through the unit, it follows that the current carrying capacity of the unit is materially increased.

, Heat fromwire IIv and distributor 22 finds its way to theouter surface of the unit and thus strip .21 also serves in the same capacity as distributor 22 but to a lesser extent. Strip 21 has a more important function, i. e., cooling theuniit .operating to substantially increase the current carrying capacity of the u'nit.`

In Figure 6 there is shown another embodiment of my invention in which the resistance device per se is preferably. substantially similar to that shown in Figure 1. Thus a fibrous strip 44 hasV wound thereabout resistance wire 48, and terminals generally indicated at 48 are connected thereto. struction to terminals I2' (Figure 4) having a connecting portion `41 embracing and clamped against wire 45 (Figure 7) and strip 44.

. The resistance vdevice comprising the strip, wire, and terminals applied thereto, 'is encased in a block of phenolic condensation product 48 or the'likea substantially similar in shape and construction to block I8 as will be seen from a comparison of Figures 4 and 5 with Figures '7 and 8.

Embedded in block 48 is a ila-t metallic strip 48 4preferably formed 'from metal having high heaty conducting characteristics. Strip .49, as vbest seen in Figures 6 and 7, is in alinement with and substantially 'parallel to fibrous strip 44' although it is separated from wire 45` and the connecting portions 41 of terminals- 48 (Figure -'1) by Bakelite so that it is amply insulated from the current carrying'parts of the-unit. As more clearly shown in Figure 6, strip 49 extends throughout the length of block 48 having horizontal portions 49a and 49h extending from the' Thus Terminals 48 maybe similar in conopposite ends oi' the block substantially parallel with the base thereof,

Another strip 50 is embedded in block 48, this strip also having high heat conducting characteristics, and occupies a position immediately above fibrous strip 4'4 (Figures 6 and 7). Strip 50 is also spaced from wire 45 and the contacting p0rtions 41of'the terminals, there being a section of block 48 therebetween. The opposite ends 50a and 58h of strip 50 are bent downwardly (Figure 6) and thence terminate in horizontal portions l50c and 50d immediately above and parallel to portions 49a and 49h respectively of strip 49.

A metal strip I, having high heat conducting characteristics, is embedded in the top of block 48 (Figures 6 and '7) Aarid has depending vertical portions 5Ia and 5Ib engaging portions 50a and 50h of the strip 50. Strip5l is preferably connected to strip 50 by suitable rivets or the like 52 and 53 extending through the respective end portions of the parts. The entire assembly, as shown in Figures 6 and 8, is preferably secured to a metal plate 54 by rivets 55 and 58 or the like passing through portions 50c and 49a and 50d and 48h respectively.

In operation, strips 49 and 50 act as heat distributors in a mam/ier substantially similar to the operation of distributor 22 (Figure 3). However, strips 49 and 50 also act as coolers for the interior of block 48 as the heat is continually conducted away from theblock and along horizontal portions 49a, 49h, 50c and 50d (Figure 6). When these portions are connected to a metallic plate, such as plate 54, an appreciable ,amount of heat is extracted from the interior of block 48. The cooling action of strips 49 and 50 is supplemented by a substantially similar action of stripA 5I which, as described above, has its portions 5Ia and 5Ib connected to strip 58. Accordingly an even temperature is maintained along the length of block 48, and block 48 is also continuously cooled when the unit is in operation, thus assur- Resistance wire 59 is wound f' about strip 51, over sheet 58, and a plurality of l terminals generally indicated at 80 are connected to the strip atvvarious spaced points therealong.-

Terminals 80 may take any suitable construction but are preferably similar to terminals I2vr (Figure el), thus having projections 8| and connectfing portions 82. Strip 51, with the wire and terminals assembled thereon, is embedded in a blockl 83 of yinsulating material, preferably a. phenolic condensation product as is tru-e o f block I8 (Figure 4) and block 48 (Figure 7).

Block 83' may take any convenient shape, a1-

though it is preferably rectangular in cross-section aslshown in Figure 10. A metallic sheathing generally indicated at 84 extends about four longitudinal sides of block 63 (Figure 10) .so that the majority of the surface 'area of block 83 is covered with metal, only the ends 83a and ^8 3b of the sheathing 84 includes on its bottom side a'pair of I longitudinal bracket-like portions 85. and 88 When operating, strip 51, which is desirablyA formed from a metal such as copper having high heat conducting characteristics, acts as a heat distributor in substantially the same manner as 'distributor 22 (Figure 4). Thus the heat along Wire 59 is substantially uniform, avoiding hot points, and increasing the capacity of the unit as described above with reference to the prererred embodiment of my invention. At the same time, sheathing 64, also formed from metal having high heat conducting characteristics, is partially acting as a heat distributor although its more important function is to cool the block 63. sheathing 64 continually conducts heat away from the block, dissipating a. portion thereof in the air and conducting another portion thereof to metal plate 68 by way of bracket portions 65 and 66 (Figure 10). Accordingly, in operation, the temperature of the resistance device is maintained substantially uniform throughout its length, eliminating hot points, and the entire block 63 is being continuously cooled, thus resulting in a resistor unit having a high current carrying capacity, as more fully described above.

Turning now to Figure l2, there is shown a further embodiment of my invention which includes a iibrous strip 69 having resistance Wire wound thereon, and terminals generally indicated at 1i applied thereto. Strip 69, wire 10, and terminals 1 iA are substantially similar in construction to the corresponding parts shown in Figure l. However, it will be understood that in every instance the resistance value of wire 10 may be varied according to the conditions under which the completed unit is to operate. y

Strip 69, with the wire and terminals applied thereto, is embedded in an insulating block 12 preferably formed from phenolic condensation product as described above with reference to block I8 (Figure 4). Thus block 12 completely encases strip 69, Wire 10, and connecting portions 13 (Figure l5) of terminals 1l. As best shown in Figure l5, terminals 1i have horizontal portions 14 extending outwardly from the connect"- ing portions and terminating in projections 15.

A metal sheathing 16 (Figures 12 and 15) having high heat conducting characteristics is embedded in block 12 and is preferably rectangular in cross-section (Figure 15). The sides of sheathing 16 are suitably spaced from wire 1l and connecting portions 1I of the terminals, this spacebeing illled with material from which block 12 is formed so that sheathing 1I is electrically insulated from the current carrying prtsf the unit. Preferably horizontal portions 14 of terminals 1| lextend through suitable apertures 11 (Figures 13 with reference to distributor 22 (Figure 4) thus making for a resistor unit havingrhigh current carrying capacity.

It will Vthus be seen that I khave provided a' practical and emcient resistor unit in which the several objects hereinabove referred to are successfully accomplished.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth. it is to be understod that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Iclaim:

i. In a resistor, in combination, 'a flat elongated strip of insulating material having a low critical temperature, a resistance conductor extending along said strip, a plurality of terminals connected to said conductor and extending away from said strip, an elongated part U-shaped in cross-section and formed from metal having high heat conducting characteristics, said strip being disposed between the longitudinal sides o1' said part and spaced therefrom so that said terminals project from the open aide of said part, and a mass of phenolic condensation product molded about said strip, said part, and the connecting portions of said terminals.

2. In a resistor, in combination, a fiat elongated strip of insulating material *having a low critical temperature, a resistance conductor extending along said strip, a plurality of terminals connected to said conductor and extending away from said strip, an elongated part U-shaped in cross-section and formed from metal having high heat conducting characteristics, said strip being disposed between the longitudinal sides of said part and spaced therefrom so that said terminals project from the open side of said part, a mass of phenolic condensation product molded about said strip, said part, and the connecting portions of said terminals, and a metallic strip extending -along the top of said mass in substantial alinement with said first-mentioned strip.

3. In a resistor, in combination, a flat elongated strip of insulating material having a low critical temperature, a resistance conductor extending along said strip, a plurality of terminals connected to said conductor and extending away from said strip, an elongated part U-shaped in cross-section and formed from metal having high heat conducting characteristics, said strip beingy disposed between the longitudinal sides of said part so that said terminals project from the open side of said part, insulating material disposed between said sides of said part and said strip, and a mass of phenolic condensation product molded about said strip, said part, and the connecting portions of said terminals.

4. In a resistor, in combination, an elongated resistance device, a plurality of terminals connected to said device and extending therefrom, a mass of insulating material having a low critical temperature said device and the connecting portions of said terminals, a pair of strips extending through said mass in substantial alinement with said device and adjacent the opposite sides thereof, the ends of said strips projecting from said mass, said strips being formed from material having high heat conducting characteriscs, and a metallic strip extending along the tcp of said mass and having its opposite end portims connected to one of said first-mentioned strips.

5. In a resistor, in combination, a dat elongated fibrous strip having a low critical temperature,arcsistancewirewmmd`abcutsaidstrip substantially throughout the length thereof, a

pluriliwottcrminalscontactingsaidwireatu t 2,218,204 spaced points and extending away from said strip,

a blocky of phenolic condensation product encasing'said stripy and the contacting portions of. said terminals, and -a pair of elongated members formed from metal having high heat-c`ond1icting characteristics extending through said'biocl; sub.. stantially adjacent the opposite sides f said strip but spaced from said' wire, the ends of said members protruding' from the ends of said-block;

6. In la. resistor, in eompiruation, a at elongated fibrous strip having. al'ow critical temperature, a. resistance wire wound about said1 strip substantially throughout` the lengththereof, a block of phenolic condensation product encasing said strip, and a pair `oi elongated members i'ormedl from metal having high heat conducting characteristics extending through said blo-ck substantially adjacent theopposite sides ofsaid strip but spaced from saidwire,v the ends of said members protruding from the ends of said block. 

